The 1967 Six Day War between the Arabs and Israel was a major event in Mideast history. Its causes and consequences remain central to the Arab-Israeli conflict to this day.

On May 15, 1967 Egypt demanded that the United Nations peace-keeping forces, in place since the Sinai Campaign, evacuate at once. UN Secretary General U-Thant, for reasons never fully clarified, complied. Then Egypt closed the Straits of Tiran and moved two tank battalions and 150,000 troops right up to Israel’s western border. A military pact with Syria and Jordan, and an illegal intrusion into Israel’s air space for surveillance over-flights of the Israeli atomic reactor in Dimona, rounded out the threats.

These were five casus belli: actions defined in international law as being so threatening to a sovereign state, that each one creates a legitimate cause for defensive military response. Had Israel retaliated with lethal force after any one of these five, its military action would have been completely legal per international law, as a legitimate defensive response to existential threats from an aggressor.

But Israel did not retaliate. It first tried political negotiations. Its complaints to the UN went unanswered. Its reminders to President Lyndon Johnson that the United States had guaranteed in 1957 to intervene if the Straits of Tiran were ever closed, or if Egypt ever re-militarized the Sinai, were ignored because Johnson was too heavily involved in the Vietnam war to consider American military action elsewhere.

After three weeks of watching the Egyptian-Syrian-Jordanian forces grow in size and strength on its borders, Israel tried one last diplomatic action, sending a written message telling King Hussein of Jordan that if he would refrain from invading Israel, Israel would not invade the West Bank. King Hussein ignored the offer.

On June 5, 1967, after receiving military intelligence that Egypt was within hours of launching an invasion via the Gaza Strip, Israel initiated its own defensive pre-emptive strike, an air attack that destroyed the air forces of Egypt, Jordan, and Syria while they were still on the ground. With control of the skies firmly in Israel’s hand, its armor and infantry put Egyptian forces to flight, reaching the Suez Canal within two days.

King Hussein of Jordan then began an artillery bombardment of Jerusalem and other Israeli cities along the Green Line. After more than a day of bombings -- which killed scores of Israelis, wounded hundreds, and caused millions of dollars worth of damages -- Israel sent a second message telling King Hussein that if he would put an immediate end to the bombardment, Israel would not retaliate for Jordan's hostilities. Hussein ignored the warning and launched an infantry invasion of Jewish Jerusalem. It was only then that Israel responded with its invasion of the West Bank.

After almost a week of Syria’s constant artillery bombardment of Israeli towns and villages in the Galilee, Israel conquered the Golan Heights, destroyed the Syrian artillery, and drove the Syrian army back to within 40 kilometers of Damascus.

Israel did not invade Egypt, although its forces could have advanced almost unopposed to Cairo. Neither did Israel cross the Jordan River, although the Jordan Legion was in disarray, with some troops having tossed their boots and rifles to more easily swim to the east bank. Nor did Israel continue its advance from the Golan Heights to Damascus, which it could have easily done. Israel stopped its advance on all three fronts after it had achieved its military objectives: the destruction of the armies that had threatened its existence, and the establishment of defensible borders.

Israel was clearly the victim of Arab aggression in the Six Day War. This is an important point with regard to the issue of Israeli settlements in, and sovereignty over, the West Bank and Gaza Strip. International law is very clear: Had Israel been the aggressor, its occupation of the West Bank and Gaza Strip would have been illegal, as would all future expansion of Israeli population into these territories.

However, as the victim of aggression, Israel’s legal position is exactly the opposite. The legal disposition of territories conquered in a defensive war can be determined only by a peace treaty between the belligerents. Absent such a treaty, the continued sovereignty and economic activities of the victim of aggression over its newly won territories is legal.

Immediately after the Six Day War, Israel offered to return conquered territory in exchange for peace. The Arab nations rejected this offer. Israel again proposed a land-for-peace deal -- with Egypt again in 1979, this time succeeding in returning all of Sinai at the Camp David I accords in 1979. Egyptian President Anwar Sadat refused to accept the Gaza Strip back, preferring that its Palestinian inhabitants remain under Israeli sovereignty.